Magnetic field sensors including a magnetic field sensing element, or transducer, such as a Hall Effect element or a magnetoresistance element, are used in a variety of applications to detect aspects of movement of a ferromagnetic article, or target, such as proximity, speed, and direction. Applications using these sensors include, but are not limited to, a magnetic switch or “proximity detector” that senses the proximity of a ferromagnetic article, a proximity detector that senses passing ferromagnetic articles (for example, magnetic domains of a ring magnet or gear teeth), a magnetic field sensor that senses a magnetic field density of a magnetic field, and a current sensor that senses a magnetic field generated by a current flowing in a current conductor. Magnetic field sensors are widely used in automobile control systems, for example, to detect a position of an engine crankshaft and/or camshaft, to detect position and/or rotation of transmission elements, and to detect a position and/or rotation of an automobile wheel for anti-lock braking systems.
The magnetic field sensor may, for example, detect a magnetic field that changes as the system operates or rotates and convert the detected magnetic field into an electrical signal for processing. As an example, the magnetic field sensor may provide an output signal having a transition or edge when the electrical signal crosses a threshold.
In many of these applications, the timing of the edge of the magnetic field detection (and the output signal) can be critical, especially in systems operating at high speed and/or systems where safety is important such as an anti-lock braking system for example. It can be important to precisely identify the time at which the electrical signal crosses the threshold. If the electrical signal is an analog signal, and the magnetic field sensor samples the analog signal at discrete time intervals, the threshold crossing will occur between samples, which can introduce sampling error and degrade the timing accuracy of the output signal.